Model-data-comparison, Lesson 2

In January, we presented Lesson 1 in model-data comparison: if you are comparing noisy data to a model trend, make sure you have enough data for them to show a statistically significant trend. This was in response to a graph by Roger Pielke Jr. presented in the New York Times Tierney Lab Blog that compared observations to IPCC projections over an 8-year period. We showed that this period is too short for a meaningful trend comparison.

This week, the story has taken a curious new twist. In a letter published in Nature Geoscience, Pielke presents such a comparison for a longer period, 1990-2007 (see Figure). Lesson 1 learned – 17 years is sufficient. In fact, the very first figure of last year’s IPCC report presents almost the same comparison (see second Figure).

Pielke’s comparison of temperature scenarios of the four IPCC reports with data

There is a crucial difference, though, and this brings us to Lesson 2. The IPCC has always published ranges of future scenarios, rather than a single one, to cover uncertainties both in future climate forcing and in climate response. This is reflected in the IPCC graph below, and likewise in the earlier comparison by Rahmstorf et al. 2007 in Science.

Any meaningful validation of a model with data must account for this stated uncertainty. If a theoretical model predicts that the acceleration of gravity in a given location should be 9.84 +- 0.05 m/s2, then the observed value of g = 9.81 m/s2 would support this model. However, a model predicting g = 9.84+-0.01 would be falsified by the observation. The difference is all in the stated uncertainty. A model predicting g = 9.84, without any stated uncertainty, could neither be supported nor falsified by the observation, and the comparison would not be meaningful.

Pielke compares single scenarios of IPCC, without mentioning the uncertainty range. He describes the scenarios he selected as IPCC’s “best estimate for the realised emissions scenario”. However, even given a particular emission scenario, IPCC has always allowed for a wide uncertainty range. Likewise for sea level (not shown here), Pielke just shows a single line for each scenario, as if there wasn’t a large uncertainty in sea level projections. Over the short time scales considered, the model uncertainty is larger than the uncertainty coming from the choice of emission scenario; for sea level it completely dominates the uncertainty (see e.g. the graphs in our Science paper). A comparison just with the “best estimate” without uncertainty range is not useful for “forecast verification”, the stated goal of Pielke’s letter. This is Lesson 2.

In addition, it is unclear what Pielke means by “realised emissions scenario” for the first IPCC report, which included only greenhouse gases and not aerosols in the forcing. Is such a “greenhouse gas only” scenario one that has been “realised” in the real world, and thus can be compared to data? A scenario only illustrates the climatic effect of the specified forcing – this is why it is called a scenario, not a forecast. To be sure, the first IPCC report did talk about “prediction” – in many respects the first report was not nearly as sophisticated as the more recent ones, including in its terminology. But this is no excuse for Pielke, almost twenty years down the track, to talk about “forecast” and “prediction” when he is referring to scenarios. A scenario tells us something like: “emitting this much CO2 would cause that much warming by 2050”. If in the 2040s the Earth gets hit by a meteorite shower and dramatically cools, or if humanity has installed mirrors in space to prevent the warming, then the above scenario was not wrong (the calculations may have been perfectly accurate). It has merely become obsolete, and it cannot be verified or falsified by observed data, because the observed data have become dominated by other effects not included in the scenario. In the same way, a “greenhouse gas only” scenario cannot be verified by observed data, because the real climate system has evolved under both greenhouse gas and aerosol forcing.

Pielke concludes: “Once published, projections should not be forgotten but should be rigorously compared with evolving observations.” We fully agree with that, and IPCC last year presented a more convincing (though not perfect) comparison than Pielke.

To sum up the three main points of this post:

1. IPCC already showed a very similar comparison as Pielke does, but including uncertainty ranges.

2. If a model-data comparison is done, it has to account for the uncertainty ranges – both in the data (that was Lesson 1 re noisy data) and in the model (that’s Lesson 2).

3. One should not mix up a scenario with a forecast – I cannot easily compare a scenario for the effects of greenhouse gases alone with observed data, because I cannot easily isolate the effect of the greenhouse gases in these data, given that other forcings are also at play in the real world.

363 Responses to “Model-data-comparison, Lesson 2”

Tom Watson, you say that haven’t heard anything that convinces you that CO2 is behind the warming. Yet, from your discussion, it is clear that you haven’t the vaguest idea of what the science is. You talk about heat transport, and specific heat as if you think convection is behind the greenhouse effect. This is not the case. All convection does is move energy from one part of the atmosphere to another. The only way energy leaves the climate system is via outgoing IR radiation–and it is here that increasing greenhouse gases has its effect. I would think that the revelation that your understanding of the physics is flat wrong might cause you to reevaluate your skepticism a bit.

Nobody’s talking about turning back the clock. The flawed premise I am referring to is the old idea (rendered much stronger by the temporal illusions of industrial society) that mankind is somehow exempt from the laws of conservation which we observe in all natural systems – that we can always build another quick fix to renew our exemption: standing apart from nature. This extremely powerful false dogma might be the most potent force blocking immediate implementation of the relatively modest suggestions of people like James Hansen.

It would not be easy to discontinue the production of power from coal (except where emissions are captured at the source) by 2030 – but compared to other challenges mankind has faced from lesser threats, it’s a modest suggestion. Hansen calls this one the sine qua non – there’s no point in discussing other measures if we can’t shut down king coal.

But I wouldn’t want a world in which the works of David Bohm, Paul Erdos and Stephen Wolfram are unavailable; and you can take my TI scientific calculator when you pry it from my cold, dead fingers!

I am do not do climate science (nor am I funded by Exxon-Mobil) but I have been running dispersion models for over 20 years (ISC, AERMOD, etc.) In that context, where these relatively simple, proven models are at best +/- 1% accurate, I have been baffled how IPCC scientists have made predictions based on infinitely more complex models that require even greater accuracy.

I also note that Spencer analyzed Aqua satellite data and concluded that there is no evidence for feedback – in fact the data shows quite the opposite. Some previously hardcore IPCC scientists have even said that Spencer is right. (Huzzah!) Perhaps I missed it, but I am surprised to find no discussion of the Aqua data on this site. Does this fall into the general category of “tell your statistics to shut up”?

I don’t know why you think you’re disagreeing with my #79. Your failure to find a trend in the HadCRUT3 data between 2001 and now adds weight to my point that there was no valid reason for the authors of the IPCC’s Chapter 9 to assert that the data for those years ‘show’ that global warming is ‘continuing’. So far as I can see, you’re agreeing with Tamino and me that the Panel’s statement was ill-advised.

I think this is an important point, worth repeating and building on a little:

#95 Aaron Lewis Says: Global warming includes the accumulation of heat in deep oceans, ice sheets, and the melting of ice. Much of the data so artfully addressed by Tamino are various measures of air temperature. As long as areas of solid ice remain as a heat sink, absorbing large amounts of heat at 0C, air temperatures may not fully reflect the rate or impacts of global warming. . . Given the highly nonlinear behaviors of ice near its melting point, we can expect that the expressed impacts of AGW (sea level rise) will be non-linear in the extreme, and may occur prior to our being able to statistically detect nonlinear effects of global warming from air temperatures.

The same goes for the oceans. When people say that there is 0.5C of warming “in the pipeline”, they’re talking about an 0.5C increase in the average surface temperature, which has increased as follows (from IPCC 4th Chapter 3):

Global mean surface temperatures have risen by 0.74°C ± 0.18°C when estimated by a linear trend over the last 100 years (1906–2005). The rate of warming over the last 50 years is almost double that over the last 100 years (0.13°C ± 0.03°C vs. 0.07°C ± 0.02°C per decade).

Based on observations of temperature and irrigation trends throughout the state, the authors demonstrated a clear irrigation-induced cooling in agricultural areas, and showed that this effect has recently slowed down.

A confirming feature of this is that irrigation has little effect on nighttime temperatures, since the cooling is due to the latent heat of evaporation of water in direct sunlight. This is not a feature that has been emphasized by skeptics other than to claim that irrigation plays a large role in the “water vapor feedback” estimation used in climate models, i.e. that models are overestimating that factor.

However, that’s just the surface temperature record. The oceans play a huge role in controlling the surface temperature over both the oceans and the continents, because of the rapid mixing of the atmosphere. In response to increased greenhouse gases in the atmosphere, a positive temperature anomaly first appears in the upper well-mixed layer of the ocean, and that signal gradually spreads into the deeper ocean layers – this is seen in both models and the global sea surface temperature record. Even if emissions are halted today, estimates are that surface temperatures would continue to rise by 1 deg C due to ocean thermal inertia (Wigley 2005 Science).

There’s large uncertainty in ocean measurements, due to poor coverage, especially of the deep ocean. Estimates are that the ocean has absorbed about ten times as much heat as the atmosphere has due to global warming. Thus, there’s a need for a complete ocean temperature monitoring network – certainly a more important goal than going to Mars. This is also why any temperature analysis that ignores the oceans and ice sheets is not going to be of much use alone in checking on climate models – but an extension of that analysis (i.e. Tamino’s) to oceans would be nice to see.

The IPCC does have an illuminating chapter on ocean observations, and the key conclusion appears to be that there is large inter-decadal variability in ocean heat content. Thus, changes in surface temperature cannot be used to infer that global warming has “paused”.

Another problem is getting accurate measurements of the exact amount of sunlight reflected by the earth, as well as the amount incident on the top of the atmosphere, since one can argue that the observed warming is all due to changes in albedo. The way around that problem was seen years ago, and it was to place a satellite at a point where it get a direct and constant view of the Earth’s surface, thereby directly measuring the top-of-the-atmosphere radiation budget. The satellite was built, and then NASA cancelled the mission under still-obscure circumstances.

Even without the climate satellite’s direct confirmation of the situation, the conclusion of Hansen et. al. 2005 hasn’t been rebutted:

Our climate model, driven mainly by increasing human-made greenhouse gases and aerosols, among other forcings, calculates that Earth is now absorbing 0.85 T 0.15 watts per square meter more energy from the Sun than it is emitting to space. This imbalance is confirmed by precise measurements of increasing ocean heat content over the past 10 years. Implications include (1) the expectation of additional global warming of about 0.6-C without further change of atmospheric composition; (2) the confirmation of the climate system’s lag in responding to forcings, implying the need for anticipatory actions to avoid any specified level of climate change; and (3) the likelihood of acceleration of ice sheet disintegration and sea level rise.

We can argue about what the eventual effect on human civilization will be, and what the cost of ending all carbon emissions and building renewable energy infrastructure will be, but the basic underlying issue is settled: we’re warming the planet.

Ref 91. Am I mistaken in thinking that “weather” represents noise, and “climate” represents signal? If I am not mistaken, then presumably a signal can have change in the slope of the temperature/time graph over time. There is no reason why the effect of climate cannot be that temperatures go through a very shallow maximum, and eventually decrease.

Ref 93. Agreed. In statistics, it is inevitable that it is hard to find the signal in the presence of noise. But standard statistical tests tell you whether you have, indeed, detected a signal. My point is that the question “What is the current slope of the temperature/time graph?” is a proper scientific question. Whether the data allows us to answer the question, because there is too much noise, is another issue entirely. But there is no reason why we cannot try.

Ref 92. Tamino writes “There’s really no evidence at all that the rate today is any different than it has been for 30 years. As for the rate temporarily seeming negative, it’s not just possible for noise to make that happen, it’s inevitable.” On this, I think we can agree to disagree. I think there is evidence that the rate today is different than it has been for 30 years. But the noise is so great that it will be some time before we will know, for sure, which of us is correct.

What is happening to temperatures now, whenever now happens to be? As of this time, now is April 2008. Or in other words, what is the slope of the temperature/time graph as of now? Is it positive or negative? It seems to me that there ought to be statistical methods to answer this question, and they probably only use data for a few recent years. I cannot see why temperatures taken 10 years or more ago tell us very much about what the slope of the temperature/time graph is as of now. My own, very limited analysis convinces me that the current slope of the temperature/time graph is negative.

Not enough information yet to say. You can’t generalize from a few months or even a few years. Sample size matters, sample size matters, sample size matters.

More CO2 in the air means a small percent surface emitted black body radiation gets absorbed even closer??

It’s not just radiation from the ground that matters. Radiation from every level of atmosphere matters as well. That’s why the carbon dioxide fraction is so important. Water vapor is more important near the ground; it has a very shallow scale height compared to the rest of the atmosphere.

Re: 96 [Response: The argument from personal incredulity is not a very useful one in scientific discussions. – gavin]

When in your personal incredulity did Einstien’s theory of relativity become science and not his personal incredulity. I see no argument presented in my post that is not both science and personal incredulity. Personal incredulity is a personal incredulity in the minds eye.

To me personal incredulity is the believe that what was written in post 96 can be dictated as certain science or certain personal incredulity. I attempt to always speak with as much logic as certain science and honesty and common sense dictates. That to me leads to the most honest science.

And to all you who count your finger and toes of temperature measurements as some form of science. The Earth is forever cooling, How CO2 slows that cooling in any process that yields an integration of stored energy over decades in the context of this earth is a fanciful personal incredulity that time and satellite measurements will demonstrate as the decades pass.

Ray #101
You say “All convection does is move energy from one part of the atmosphere to another. The only way energy leaves the climate system is via outgoing IR radiation–and it is here that increasing greenhouse gases has its effect.” True, but when water evaporates from the ocean surface the ocean cools. This heat is released high in the troposphere when the water condenses. Does this convection process not largely bypass the greenhouse gases in the troposphere and allow relatively more IR to go out to space?

Jim Cripwell, you’re illustrating exactly what students go through in trying to understand statistics, re:
> the slope of the (climate, signal) temperature/time
> graph, as of now (April 2008)

Yes, there is evidence that will let us say what that slope is as of April 2008. It will be available.

But it isn’t available now.
You can’t get “now” from statistics.

Urge your congresspeople to put the Triana satellite up, so we can at least have contemporary data for the planet. Put an end to teaching the “controversy” by collecting actual information to inform choices.

It’s not just radiation from the ground that matters. Radiation from every level of atmosphere matters as well. That’s why the carbon dioxide fraction is so important. Water vapor is more important near the ground; it has a very shallow scale height compared to the rest of the atmosphere.

Tom’s reply: I do not believe any science shows “vapor is more important near the ground; it has a very shallow scale height compared to the rest of the atmosphere.” as a complete and overriding law that governs.

convection transport may slightly increase as CO2 increases because initial absorptions is more intense. In the design of a heat exchanger the most effective way to transport the most heat is to have the hottest meet the coldest first. In effect Adsorption in a shorter distance create a mini change in temp and density for the initial start of convection.

And in cold dry places or any dry places the Earth cools by degrees per hour when the sun goes down. Any heat that gets to a cool dry place in the atmosphere is gone very very quickly. And infrared heat that’s up cannot get back down as it’s blocked by CO2 and water vapor below.

My Personal incredulity says the CO2 does not effect the altitude at which heat that is above can get below it and will be lost to space. CO2 increasing may have some minor effect in getting heat above that altitude in some tiny tine amount. Or maybe on balance is slows it some tiny tine tiny amount. But whatever will not create any real difference in what ever is defined as the global temperature.

And I read your stuff on Greenhouse 101: Science looks OK but makes no case for any CO2 suppositions.

Ref 117. Hank. I dont agree with you, but let us assume you are correct and “Yes, there is evidence that will let us say what that slope is as of April 2008. It will be available. But it isn’t available now.
You can’t get “now” from statistics”. (As an aside, I am Canadian, and we dont have Congressmen.) But if we dont have any “now” statistics, then I have trouble with the latest magazine from National Geographic, a Special Report on Changing Climate. On page 25, it is stated “Here’s another indisputable fact: Earth’s temperature is going up too”. Surely this statement is just plain wrong, if you are right. How can it be “indisputable”, if there are no “now” statistics? Obviously, if you are correct, we have no idea whether the earth’s temperature is still going up, despite the fact that CO2 concentrations are going up at an unprecedented rate.

The six years of data used by the IPCC don’t rule out continued warming, but neither do they show it. Please refer to the post ‘Rahmstorf et al 2007 IPCC Error?’ at the Niche Modeling blog, and the ensuing discussion.

Re #116 B Buckner: yes, convection plays a very important role for outward heat transport. Both wet convection in the lower troposphere, and dry convection higher up. But the question to ask is how this affects the response of the system to a change in greenhouse gas concentration.

Convection interacts with the greenhouse effect in the following way: a convecting atmosphere establishes an adiabatic lapse rate of some 5-6 degs per km of height. At some level in the troposphere — on average 6 km but dependent on wavelength — the air changes from opaque to transparent for the heat radiation, and from that level, the heat escapes to space.

As I like to depict it to myself, if you increase the CO2 content of the air, the air’s opaqueness for IR increases, and this “radiating surface” will creep up. (It’s a bit like the “wall” of fog coming closer when the fog thickens.) This means that the temperature of the radiating surface will drop, because of the lapse rate. According to Stefan-Boltzmann, the radiating effectiveness drops, and the whole Earth-ocean-atmosphere system has to warm up to compensate.

In reality it’s more complicated of course; the CO2 in the air throttles only a part of the outgoing heat in this way, much also leaves from the top of the “wet layer” or even from the surface. And also the profiles of the spectral lines get broader, which contributes its own effect. Etcetera :-)

Jim, Tamino’s 92 answers your 119. I’m not going to dispute the question of “undisputable” — email National Geographic’s editors for that argument. Tamino makes the point much better than the N.G. stuff you set up to knock down there. You can find bad writing everywhere.

I would be grateful if you would clarify for me a puzzling aspect of the your Rahmstorf et al. ’07 Science paper. You state in the figure caption that the ‘minimum roughness criterion’ was used to get the temperature trend line. Use of this method of data padding as described in Mann 2004 should ‘pin’ the trend line to the 2006 temperature value. However, while the 2006 value lies in the center of the IPCC range, the trend line shown on the figure lies above the 2006 value, in the upper IPCC range.

I would like to clarify this apparent inconsistency. This is an important paper for the case that ‘the climate system may be responding more quickly than climate models indicate’ and it is important to verify its technical correctness. More details and graphs can be found here:

[Response: Thanks David. I have responded to your query also on your website, as follows:

1. The smoothing algorithm we used is the SSA algorithm (c) by Aslak Grinsted (2004), distributed in the matlab file ssatrend.m. This has two alternatives for the boundary condition: (1) minimum roughness (which is what we used in our paper) and (2) minimum slope. This is described in the Moore et al. paper. If you have questions about the details of this algorithm please contact its authors. I think the confusion that arises is that you equate “minimum roughness” with “padding with reflected values”. Indeed such padding would mean that the trend line runs into the last point, which it does not in our graph, and hence you (wrongly) conclude that we did not use minimum roughness. The correct conclusion is that we did not use padding. Note that Moore et al. call their minimum roughness “a variation” on the minimum roughness criterion described by Mann (2004). This already makes clear it is not the same.

2. None of the conclusions of our paper depend on the use of this particular boundary condition at the end, which only affects the last five years of the trend line. As you can see, the temperatures 2002-2006 lie in the upper half of the IPCC range.

(Btw. – my name is Stefan Rahmstorf. You get my first name wrong here and my last name wrong on your site, just like Pielke consistently mis-spells my name in his Nature Geoscience correspondence – this is also an indication of the care someone takes in getting things right.) – stefan]

Ref 122. Hank, you are missing the point of my discussion. I explained many months ago, that the reason I post on RC is because people here challenge my ideas, and as a result, I understand better what I am talking about. This does not happen on CS. This idea started with Tamino’s #67, in which he discussed the idea that warming ceased in 2001. The point I started off with is that I do not question that global temperatures have risen. However, what I see in the media particularly, but in many different other places, is the idea that temperatures are still rising. This is not, as Ray Ladbury thinks, a question of the difference between weather and climate. If we consider what I will call “climate temperature”, what, I think, needs to be established is whether climate temperature is rising, staying stable, or falling, again going back to Tamino’s #67. From the discussion on this blog, there seem to be two possibilities. Either there is not enough evidence to say what is currently happening to climate temperatures, as you seem to believe. In which case no-one knows that climate temperatures are rising. Or there is enough data, which I believe, and I believe climate temperatures are falling. I am trying to find someone who will dispute this, and show me a scientific, hopefully peer reviewed, paper which establishes that climate temperatures are, indeed, still rising. However, no such paper seems to exist.

Re Jim @ 100 Let us assume most understand radiative physics. Now the reiteration of blackbody radiation over time as it applies to higher altitudes is not well explained anywhere. As warm air and the heat it contains rises, there is a point where there is more CO2 and H20 below it than above it. All radiation that is emitted up and not adsorbed is gone in less than the blink of an eye. All that is adsorbed by CO2 or H20 is instantly conducted to the 97 to 99+ percent of non CO2/H20 air molecules. For whatever temperature works out, the warmed air re radiates a spectrum and all of that spectrum that is not adsorbed and pointed up is also gone in less than a blink of an eye.
That which is emitted in a downward direction will be adsorbed and maybe reflected back up if it hits clouds.

Where air is dry it cools by degrees per hour when the sun is not shining.

My gut or my experience has my personal credulity suggesting there is an inclination or the sum of all factors gets the radiative energy out to space and CO2 has no property in the context of it’s rare content the Earth’s atmosphere to move temperatures up or down more than a tiny tiny tiny amount.

Noise exists in the global climate system; you can call it “weather” if you like. But because noise exists, it will never be possible to determine the instantaneous long-term rate of change; that implies letting the time span over which a determination is made shrink to zero.

You also propose a false dichotomy when you say “I believe climate temperatures are falling,” then ask someone to dispute it by showing a “paper which establishes that climate temperatures are, indeed, still rising.” I dispute that temperatures are falling, not because I can prove they were rising over the last six or seven years, or six or seven days, or six or seven minutes, but because there’s zero evidence for your claim. I’d never get this published by a reputable journal because it’s so obvious that noisy data over a very short time span don’t support *any* conclusion at all.

Both physics, and the long record of temperatures, support the “still rising” hypothesis, but you seem to think that because you can find a time span which is short enough to give an inclusive result, that justifies a conclusion of cooling. You don’t seem to realize that noise making the short-term trend *seem* negative even though it’s still positive, isn’t just a possibility, it’s an inevitability. If the temperature record did not contain episodes like we’ve seen recently, brief time periods with negative-but-not-statistically-significant trend rates, then I’d know that the data are invalid.

It’s really like flipping a coin to test whether it’s fair. Even if it is, if you flip it enough times eventually you’ll see 10 heads in a row. In fact, if you flip it enough times and don’t see 10 heads in a row somewhere, then you have proof that the coin is not fair.

Your entire premise really is no different than the claim that “global warming stopped last Thursday.” Of course the data don’t disprove that idea. But it sound ridiculous, because it is.

Jim Cripwell (123) — I’ll say that a ‘climate temperature’ is a 50 year linear trend line. Since you are interesteed in ‘now’, use the data from 1958 CE through 2007 CE. Fit the data linked in comment #120 to discover an upward trend line. By this definition of ‘climate temperature’, it is rising.

#123 Jim Cripwell: another thing to contemplate. Can you see your toenails growing? No? Look back in a week. Not yet? Have your toenails stopped growing? Or is the growth too small to measure?

However, if you last clipped them 6 months ago, you should have have evidence that some time between then and now, they have grown enough to tell the difference.

If despite this evidence you are still convinced that because you can’t actually see them growing, they must have stopped, measure their exact length to the best accuracy you can, and report back here in 6 months (with no clipping before then obviously).

Why is this relevant? Aside from the noise issue, the rate at which temperatures are growing is pretty slow. If for example we have a rate of increase of 3°C over a century, that’s 0.3°C per decade. If you just look at a few years, the change will be within the error bars (and very likely dwarfed by natural variability aka “noise” — do toenails shrink and expand depending on the tightness of your shoes?).

Should anyone be saying temperatures are still rising given this? It would be more accurate to say something like you can’t judge anything by looking at a few years in isolation, but there’s no evidence of a change in the trend because we are still well above the pre-AGW level — but how, I wonder, would that have been spun by the denialosphere?

Goes-12 has 4 IR channels: the shortwave infrared channel (3.8-4.0 um) and two longwave infrared (10.2-12.5 um) channels have a resolution of 4 km, while the water vapor channel (6.7-7.0 um) has an 8.0 km resolution.

Regarding the “arrogance” discussion – Laypeople don’t have the time or education to evaluate scientific claims based on the scientific data, especially in a field as complex as climate science. We have to rely on the judgment and expertise of scientists who attempt to explain complex analyses in simplified ways we can understand. Therefore it is essential for laypeople to judge the character and motivations of a scientist making a claim, in order to establish in their mind whether this person is a trustworthy authority.

As a layperson, I suggest that scientific claims and scientific authorities cannot be reliably evaluated by any means except how consistent they are with evidence.

Also, some facts about climate, in spite of its complexity, are simple. One such fact is that, since IR-excitable gases like CO2 warm the atmosphere, increasing their concentration forces the temperature to increase. No matter what guesses you make about the “character and motivations” of people who mention that fact, it remains true. Personal considerations do not affect arithmetic.

Please make the time to look at the evidence. The lives of our children may depend on it.

If a goal of realclimate is to inform laypeople of issues in climate science, then arrogance in this forum will only appeal to its most unquestioning adherents while driving away those who prefer to keep an open mind about a complex and dynamic field.

That is good advice. Many of us who are aware of the evidence that our emissions warm the globe tend to say things that doubters and newbies perceive as arrogant.

In my case, however, and probably that of others, these apparently arrogant comments really reflect great despair at the peril ahead and the stubborn gullibility displayed by many who refuse to face it. Denialism has won every round of this debate so far, no matter what debating tactics have been tried against it. Precious years have been squandered. Far from being curtailed, emissions are rising. The likely cost is painful to imagine and could be much more painful to experience.

The Earth is forever cooling, How CO2 slows that cooling in any process that yields an integration of stored energy over decades in the context of this earth is a fanciful personal incredulity that time and satellite measurements will demonstrate as the decades pass.

To which I have no answer, because I can’t for the life of me figure out what you’re trying to say here.

Tom’s reply: I do not believe any science shows “vapor is more important near the ground; it has a very shallow scale height compared to the rest of the atmosphere.” as a complete and overriding law that governs.

It’s an empirical observation, and it’s theoretically backed by considerations such as the Clausius-Clapeyron law. The scale height for the atmosphere in general is about 8 kilometers. For water vapor it’s closer to 2 km.

convection transport may slightly increase as CO2 increases because initial absorptions is more intense.

In the design of a heat exchanger the most effective way to transport the most heat is to have the hottest meet the coldest first. In effect Adsorption in a shorter distance create a mini change in temp and density for the initial start of convection.

Huh? What? Come again?

And in cold dry places or any dry places the Earth cools by degrees per hour when the sun goes down. Any heat that gets to a cool dry place in the atmosphere is gone very very quickly. And infrared heat that’s up cannot get back down as it’s blocked by CO2 and water vapor below.

It doesn’t have to get all the way down. It just has to get to the next layer below it and heat it up a bit. Then that layer will radiate a bit more both up and down. Every layer affects every other layer, but not always by a direct connection.

My Personal incredulity

Your personal incredulity is meaningless for convincing anybody else of anything. “Personal incredulity” means “what this person can’t believe.” And what you believe doesn’t matter; what you can prove or demonstrate does.

says the CO2 does not effect the altitude at which heat that is above can get below it and will be lost to space. CO2 increasing may have some minor effect in getting heat above that altitude in some tiny tine amount. Or maybe on balance is slows it some tiny tine tiny amount. But whatever will not create any real difference in what ever is defined as the global temperature.

But it does.

And I read your stuff on Greenhouse 101: Science looks OK but makes no case for any CO2 suppositions.

CO2 largely allows visible light to pass but absorbs infrared light. Thus more of it in the atmosphere will heat the atmosphere, which will heat the ground. There’s really no way around it.

climate science is quite new and would need quite a few years before it establishes any reputation. A “Reputable journal” as mentioned above should be judged in this context.

Evangelista Torricelli invented the barometer in the 1600s. Jean Joseph Fourier posited the existence of the greenhouse effect in 1824. John Tyndal showed that it was mostly due to water vapor and carbon dioxide in 1859. In the 1860s, Louis Agassiz established that there had been ice ages. The first prediction of warming under doubled carbon dioxide was published by Svante Arrhenius in 1896.

Climatology is not a new field. Newer than physics, yes. But much older than, say, computer science, or quantum mechanics.

Given your response to some comments referring back to our previous discussion comparing protein modelling vs climate modelling I thought I’d give you an update on progress here. It might amuse you. Or not.

Well basically, I threw the debate open to the modellers here and to be honest all hell broke loose. With a 5-1 margin (not including myself) the tv chemists here came back with “well they would say that; it’s all rubbish if you ask me” etc etc. In effect the conclusion was that protein folding was not a fair comparison (my mistake then eh!) and that “docking scores” was a more appropriate comparison. If you are interested in what that is then just google it. Personally, it quickly went past my head but the end result was that a major pharma company now has climate model code running on its cluster (disguised as something else of course). I’ve stopped asking about it since it is only more fuel to the fire.

For my part, I’ve done a bit more reading and whilst I am comfortable with the differences, I am plauged by nagging doubts about the fidelity of the prediction which is kinda what’s be discussed again on this post. I think that’s driven by the fact that many of the discussions are heavily focussed around physical methods (or a physics perspective if you like) and I worry that the problem has much larger chemical and biological components than is being suggested. And from brutal experience I know that once you start working a multiple discipline boundaries things get complicated and just a little bit messy. On the plus side that means it’s a fabulously interesting area to work in. I’m almost jealous! And you’ve got a bunch of comp chemists running code on a big pharma cluster. I’ll let you know if they actually get a conclusion…

Also, some facts about climate, in spite of its complexity, are simple. One such fact is that, since IR-excitable gases like CO2 warm the atmosphere, increasing their concentration forces the temperature to increase. No matter what guesses you make about the “character and motivations” of people who mention that fact, it remains true. Personal considerations do not affect arithmetic.

[Response: Your paper is wrong, wrong, wrong. All of these effects are included in all the standard methodology and when you do the full calculation – using all the spectral lines, using full atmospheric profiles, using all the spatial information you end up with the the standard number – i.e. 2xCO2 gives ~4 W/m2 forcing. You can continue to point to special cases that don’t use all the lines, that don’t use full profiles and that don’t integrate over the surface of the planet, but they won’t change the numbers you’d get if you did. There are real uncertainties in climate science – the role of aerosols, clouds, ice sheet response etc., I would advise focussing on them, and not on physics that has been known and properly calculated for decades. – gavin]

Stefan, I’ve never found where the IPCC FAR has included any model uncertainty, in their ranges, such as those in the figure you reproduce. Those ranges are based on uncertainties in forcings and scenerios, and not model uncertainty. If using multiple models are intended to be a proxy for some analysis of model uncertainty, I haven’t found where the FAR explicitly discusses and justifies it. I also don’t see how such a proxy would account for the correlated errors among the models that was brought to Working Group I’s attention.

Maybe there is not enough good data yet to validate the models to a small enough uncertainty to attribute and project the less than 1W/m^2 of globally and annually averaged energy imbalance responsible for the recent warming. The wide variation in model sensitivities that can “match” the 20th century climate despite correlated errors and poor reproduction of the signature of the solar cycle indicates that we are not there yet.

As warm air and the heat it contains rises, there is a point where there is more CO2 and H20 below it than above it.

Those are actually two different points, since despite your disbelief, H2O does indeed have a much lower scale height than CO2. But, let’s combine them for the moment and agree that there is such a point, knowing that it will have to be somewhere below the scale height of H2O.

All radiation that is emitted up and not adsorbed is gone in less than the blink of an eye.

Yes, self-evident. You can dispense with the ‘blink of an eye’ phrase. Where time comes in to it is how long the energy is resident in the atmosphere before it is not absorbed and escapes to space. Because that’s what greenhouse gasses do, they increase the time it takes for heat energy emitted by the surface to reach space. The atmosphere then warms until the outgoing rate equals the rate solar energy reaches the surface.

All that is adsorbed by CO2 or H20 is instantly conducted to the 97 to 99+ percent of non CO2/H20 air molecules.

No, it is not. Only a portion of it is conducted to the 97 percent of non-greenhouse gas molecules through collision, the rest is spontaneously emitted and then absorbed by other CO2 or H2O (or CH4 or NOx, or CFC, etc) molecules, and then emitted again. And so on. Any single emission can go up, down or sideways. Down keeps the energy in the system. Depending on the altitude, sideways also is likely to keep it in the system. Only up has a chance of making it to space without further absorption, but even up has a chance of absorption, and then subsequent downward emission.

My gut or my experience has my personal credulity suggesting there is an inclination or the sum of all factors gets the radiative energy out to space and CO2 has no property in the context of it’s rare content the Earth’s atmosphere to move temperatures up or down more than a tiny tiny tiny amount.

Yes, the radiative energy DOES eventually get out to space, and that’s a very good thing, but increasing CO2 in the atmosphere does in fact raise the point at which more energy is emitted to space then is emitted back down. Why? because H2O is not increasing, or hasn’t been, but CO2 (and CH4, NOx, CFCs, etc) has been, and adding more CO2 raises your point where there is more CO2 and H20 below it than above it.

In addition to gavin’s response about the line-by-line calculations your paper appears to have a major error in the modelling of clouds. You say:
“Clouds are different than water vapor. They form when water vapor condenses into its liquid or ice state. Being virtually opaque to infrared, they are a much stronger absorber and radiator of heat than water vapor or any other gas in the atmosphere and this occurs basically over the full wavelength spectrum of interest. Furthermore, because they are opaque, all of their radiation (based on their temperature) goes back to Earth, while for greenhouse gas radiation only half up goes down and the rest up. ”

This is incorrect, the tops of the clouds will radiate upwards with a black body signature appropriate to their temperature, satellite images showing the IR radiation from the tops of clouds can be seen everyday on the Weather Channel, for example.

Below is the calculation using MODTRAN of the condition used in your Fig 2:

Re 138 – Tom, if you feel you have an analysis that overthrows the current understanding of climate science, then by all means you should submit your paper to a peer-reviewed journal, such as Science. That is how such issues get resolved. Making bold assertions here, then referencing your own unpublished paper is an effort to circumvent the way science is done. (I was unable to access your site to see the paper – apparently you are in server overload.)

Thanks for the update! If a pharma company is running “climate code” that is amusing.

I’m not quite sure I understand the feedback from your chemists.

“In effect the conclusion was that protein folding was not a fair comparison (my mistake then eh!) and that “docking scores” was a more appropriate comparison. If you are interested in what that is then just google it.”

My discussion was intended to illustrate the fact that models had a wide range of characteristics, and that protein folding was almost as far away from climate modeling as you could get. [EDA logic simulations are probably even further.]

Hence, when they say: “not a fair comparison”, do they mean, they are agreeing they are very different, or disagreeing with comparing them? I assume they mean that docking scores are more like climate models, and I’ll have to think about that. I’d forgotten those, although they were explained to me ~10 years ago by pharma chemists, or maybe one of our SGI computational-chemistry gurus.

Surely someone has done a good taxonomy of simulation models, but I can’t point to one offhand. I do know that lots of people assume that their kinds of models they do are representative, which may or may not be true.

Finally, maybe the owners of this blog might care to say more about chemistry and biology effects in the models, or bounds thereon.

I never cease to be amazed by the people who, despite having no knowledge of climate science in general or of the science of anthropogenic global warming in particular, appear sincerely convinced that they, and they alone, have discovered the Simple And Obvious Reason why global warming due to anthropogenic CO2 emissions is physically impossible — a Simple And Obvious Reason which has been missed by all of the hundreds and hundreds of climate scientists who have studied these matters for decades.